One of the most common bacterial infections is that of the urinary tract. Patients who need rapid diagnosis of urinary tract infections (UTIs) include premature newborn infants, prepubertal girls and young boys, sexually active women, elderly males and females, pre-operative patients, patients with chronic disease, patients with neurological disorders, patients with genitourinary congenital disorders including urethral valves and reflux, patients with sickle cell disease, patients with renal disease and polycystic kidney disease, patients having undergone renal transplantation and pregnant patients. The diagnosis of UTI in the elderly and in infants, in particular, is difficult because of different signs and symptoms and the inability to communicate.
One technique for diagnosing UTI involves measuring the level of pyuria (the presence of leukocytes in the urine). Leukocytes are normally present in urine, and careful studies have established that the threshold limit for pathological pyuria is about 1×104 leukocytes per milliliter of uncentrifuged urine. Pyuria correlates closely with acute symptomatic infection, and its presence may thus warrant further study of urine specimens in which microorganism counts are less than accepted threshold levels. Several methods have been developed for assessment of pyuria. One such method involves the detection of leukocyte esterase, which is an enzyme released by white blood cells. For example, dipsticks based on leukocyte esterase have been developed that contain an area predisposed with reagents. The test sample is spotted onto the area so that the enzyme reacts with the reagents, thereby inducing a color change. Unfortunately, such test methods generally require that a controlled reading window. However, it is not always feasible to carefully monitor testing, particularly in consumer-based applications.
As such, a need currently exists for an improved technique for detecting an enzyme in a test sample.